Preparation And Applications Of Graphene-Based Composites （Graphene/GO And GO/MoS₂/TiO₂）

Graphene is one of the most promising carbon nanomaterials because of its exceptional electronic, optical properties and high charge carrier mobility, etc., so the preparation and application of graphene-based composites are still research priorities. Considering the intrinsic defects of the single-phased nanomaterials, the preparation of hybrid nanomaterials, which combine the unique properties of individual nanostructures, can make their performance and applications a breakthrough, due to the synergistic effects between different materials.However, the insolubility of graphite has become a big obstacle for the preparation of graphene and functionalized graphene-based composites. Graphene oxide（GO） is a type of water-soluble material, and the introduction of oxygen-containing groups endows GO with many intriguing surface chemical properties. For example, its amphiphilicity and negatively charged nature derive a simple and green interface self-assembly technique; its solubility and two-dimensional flexibility simplify the production of functionalized graphene-based composites. Due to these desirable properties, GO can be viewed as an unconventional 2D soft material and suitable for several methods to prepare graphene-based materials. The as-prepared materials, which are applied to the field of electrochemical application and photocatalyst, have gained wide attention. My work mainly includes:（1） We demonstrated an effective and one-step technique to assemble graphene-based thin films with assistance of GO, and the films were formed at the interface of phase-separated mixture of water and n-heptane. In the process of exfoliating graphite powder, graphene oxide played the role of a macromolecular stabilizer and was able to interact with the surface of graphite, making graphite powder functionalized. Then graphite powder can be dispersed and exfoliated better. After adding n-heptane, graphene oxide formed Pickering emulsion at water-oil interface as an emulsifier, and assembled at the interface to minimize the interfacial energy along with the exfoliated graphene nanosheets. Finally, the self-assembled graphene-based film was formed, and the transparency and conductivity of thin film were also tested.（2） We prepared graphene-based ternary heterostructure composite by solvothermal method, with layered GO/MoS₂ mixture as cocatalyst. By changing the amount of cocatalysts, and the proportion of GO and MoS₂, a series of different composites were synthetized. Meanwhile, the photocatalytic performance of the composite materials with different cocatalyst content was investigated. The results showed the as-prepared composites had effective photocatalytic performance and good stability. Therefore, graphene and MoS₂ nanosheets worked as cocatalysts in the field of photocatalytic hydrogen generation. They had positive synergistic effects, including suppression of charge recombination, and an increase in the number of photocatalytic reaction centers. This study is feasible for the development of noble-metal-free photocatalyst, and has a great potential for photocatalytic application.